The present invention relates to an improved composite closure cap of the type used for sealing containers and particularly plastic containers. More particularly, the invention relates to a composite closure which is especially useful for sealing plastic containers which have been formed by molding or vacuum forming methods.
Many products, and particularly many food products, have been traditionally packaged in glass or metal containers which are relatively expensive as well as often being relatively heavy. More recently there has been a development of other types of containers and one such container comprises a relatively thin plastic container which is either molded or vacuum formed. These containers are characterized by extremely thin walls and light weight so that they present a number of different problems related to their sealing with closure caps. The closure cap and the related package finish of the invention are particularly useful on these thin wall plastic containers. The closures are not only characterized by their ability to provide an easily formed and effective seal, but also by their ease of manufacture and their ability to provide a vacuum indicator where the closures are used in vacuum sealing procedures.
The closure cap of this invention and the related container finish are particularly useful upon inexpensive food packaging such as baby food packaging where the products are distributed in millions of packages per day requiring a simply manufactured and easily filled and sealed package. In addition, the closure cap is useful for baby food products where the user has occasion to open and then re-seal the package.
It is characteristic in vacuum sealng these thin-walled plastic containers to use a lesser vacuum than has been traditionally used with the glass and other thicker walled containers and the closure cap of the invention provides an effective vacuum indication even with a relatively low vacuum.
Another advantage present in packages of the invention sealed with the improved closure cap is the ability of the sealed packages to provide vacuum indication during an exposure of the sealed package to pressure changes, including those experienced where packages are transported through or to high altitude locations.
Accordingly, an object of the present invention is to provide an improved closure cap and sealing finish for a plastic package.
Another object of the present invention is to provide a closure cap particularly adapted for sealing thin-walled plastic containers.
Another object of the present invention is to provide an improved gasket and method of manufacture for a closure cap.
Another object of the present invention is to provide an improved cooperating container finish and closure cap for being applied thereto, particularly for thin walled plastic containers.
Other and further objects of the present invention will become apparent upon an understanding of the illustrative embodiments about to be described, or will be indicated in the appended claims and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.